So much Tech and so little time

We had some issues a while back where there was latency between a PC and SAN so I started to look at all the layers to try and find a problem, here’s my findings in case anyone finds it a interesting read.

To rule out the PC, I’ve tested the performance of the SAN and network throughput.

The performance of the SAN which is based in IOP’S (Input/Output Operations Per Second) and the current average total is 800 (found on the SAN info page). To put this prospectus, a poor performance would be in the 2000’s.

The below graph only shows output from 17:28 but has been running all day meaning the average should be accurate:

Looking at the performance of switches can be difficult, but we’ve started using HP Intelligent Management Centre which is great at collating stats. The switches reported low bandwidth, CPU, memory and I/O seemed normal:

We know from experience the throughput on these switches is limited by infrastructure in our case 1GB fibre.

These are the theoretical Max Sequential (SEQ) write limits we could obtain from our connection to the SAN (in practice there is a 5%-20% overhead involved):

I’ve managed to very roughly test this write limit from a client to the SAN SAS disks:

A result of 81.12MB/s is very positive, considering we can realistically over ever achieve 125MB on our current setup.

What this meant in my opinion was the SAN and network were not to blame meaning it was either client or server….Long story short the AV on the server was causing our latency not the “network”.

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